Tuesday, December 15, 2009


Recycling and reuse of greywater raises issues of pollution at the percolation level based on cleaners used by the household. A UCLA report writes: "The state revised 2007 California Plumbing Code has now eased previous permit requirements for certain untreated graywater delivery and distribution systems. Permit requirements are now based on daily discharge volume, number of household sources, and number of graywater system fixtures. According to the Draft 2010 California Plumbing Code proposed by the California Department of Water Resources expanded indoor and outdoor uses of graywater (e.g., toilet flushing, spray irrigation, etc.) are also possible if the source graywater is treated to meet the California Department of Public Heath statewide uniform criteria for disinfected tertiary recycled water. This implies that, for expanded use graywater (i.e., besides in underground irrigation systems), water quality of treated graywater from small-scale, on-site residential treatment systems would be held to the same regulatory standards as large-scale, centralized municipal water treatment plants."

Permitting greywater can lead to a number of benefits
- Shows an awareness of the toxic problem which until now is unaddressed

- May not be a problem at all if the average person is not growing anything.

- Localizes the pollution problem from what people use for cleaners. This will form a layer at where the water percolates into the soil. If toxic cleaners are used then vegetables should not be grown with this water. Fruit trees which get water from a deeper root system are ok. And over time the percolation layer would need to be aerated so that anaerobic bacterial process can deteriorate the polluted layer.
However note that localizing the pollution source means that greywater (toilet is black water) does not pollute the larger water bodies like the Bay and Belmont Creek.

- Provides an incentive for growers to shift to organic and bio degradable cleaners

- expands the market organic and bio degradable cleaners so that these products can be competitive or lower cost than toxics.

- Reduces the amount of water that needs to moved around the region. Landscape uses the same amount of water as interiors for single family homes (5% each of total freshwater.) In Multifamily homes interior use is 3% of total and external use is 1%! Water movement accounts for 30% of energy use. Reducing demand improves availability and energy efficiency.

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